1. Field of the Invention
The invention relates to a process for separating hydrophobic organic liquids, such as oil, from water. A mixture of water and hydrophobic organic liquids is placed in a column-like vessel which has been loosely filled with a hydrophobic, preferably open-celled, polyurethane foam. The water will flow through the foam material, but the hydrophobic organic liquid will be absorbed by it. When the foam becomes covered and saturated with the hydrophobic organic liquids, it is pressed to extract the hydrophobic organic liquid so that it can be reused.
2. Description of the Prior Art
The extraction of hydrophobic organic liquids from water, such as the extraction of crude oil from water, is very important to the preservation of the environment. Water in the environment may become contaminated with hydrophobic organic liquids as the result of accidents at sea, and when oil-containing ballast water is pumped from oil tankers.
The traditional methods used to separate hydrophobic organic liquids from water involve mechanical means based upon gravitational separation. The problem with these methods is that they require a large amount of time and space.
The prior art teaches that open-celled foams of polyurethane, urea formaldehyde condensates, polystyrene, cellulose, acetate, and other materials can be used to absorb oil from water surfaces. U.S. Pat. No. 3,779,908 teaches that flexible open-celled foam can be used to separate oil from water. The mixture of oil and water is allowed to flow through the foam where it is absorbed. Moreover, U.S. Pat. No. 3,886,067 teaches that oleophilic semi-rigid to rigid foams can be distributed on oil-containing water surfaces to absorb oil. The foams are then removed after absorption. The problem with the foams disclosed in these and similar patents is that they only had slight oil absorption capacities.
U.S. Pat. No. 3,681,237 teaches that the oil absorption capacity of foams can be increased if they are coated with hydrophobic agents. The coatings, however, are washed away relatively quickly and, thereby, rendered ineffective. German Patent Application No. P 2738268.9 teaches that hydrophobic compounds can be incorporated into the structure of the foam in order to increase the oil absorption capacity of the foam. Lipophilic compounds are used as the hydrophobic compound. The density of the foam produced is from 8 to 25 grams per liter and the ratio of closed to open cells is from 3:30 percent to 97:70 percent. Because the foams have such low densities, they are reversibly deformable only on a limited scale. Consequently, they can be pressed out and reused only on a limited basis resulting in higher costs.
Another major problem with the foams disclosed in the prior art is that they permit a low rate of flow-through and quickly become plugged by the oil or other hydrophobic liquids. Such high flow-through velocities are needed for practical usage, especially for pumping out ballast water and removing oil spills, methods had to be found to eliminate this problem.